Tachometer.



:PETRUS VAN SANTEN KOLFF, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 THE ELECTRIC TACHOMETER CORPORATION, A CORPORATION 0F DELAWARE.

TACHOMETER.

Patented May I4, 1918.

Application led May 2, 1916. Serial No. 94,929.

To -aZZ whom t may concern:

Be it known that I, PnTRUs VAN SANTEN KOLFF, a citizen of the United States of America, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Tachometers, of which the following is a specification.

This invention relates to electrical speedindicating mechanism, and particularly to that type in which an electric generator is driven by the shaft whose speed is to be indicated, the speed values being indicated by the scale deiiections of a volt or milli-volt meter connected to the electric generator.

The main object of the invention is to provide a mechanism in which, by the use of a suitably selected variable speed-change gearing, many of the electrical and mechanical difficulties of the present type of indicating mechanism are' obviated.

In the previous types of speed-indicating mechanisms, where the speed ratio between the main spindle and the armature shaft is constant, the following objections are noticed (A) When Calibrating these old types of magneto-generators, in conjunction with a volt meter, having two orvmore scale ranges of speed, it is necessary to calibrate for each separate scale range, which is usually effected by inserting in series with the electrical circuit a certain amount of manganin resistance wire and adjusting the quantity of lthis wire so that at a known speed of the magneto generator the reading on the volt meter exactly corresponds to this speed. In

, other words, if the old type of magneto generator were to be calibrated to the volt meter with three scale ranges, say in the ratios of one to four to sixteen, it would be necessary' to form three circuits between the magneto generator and the indicator, each circuit including the indicator circuit having a resistance proportionate to the value of the scale range. As each circuit would consist partly of copper and partly of manganin wire, and as copper has a wellknown temperature error, whereas-manganin wire has practically no temperature error, it is evident that such a tachometer would show various temperature errors when used at the same temperature over all three scale ranges.

0n the other hand, in my type of speedindicating mechanism with variable speedchange gearing between the shaft and the magneto-generator, the scale ranges are in absolute proportion to the speed ratios between the main spindle and the armature shaft which speed ratios are obtained by means of the speed changev gears. It is therefore evident that the speed of the armature shaft, corresponding to full scale deflection on the indicator, for any of the three 'speed offlOOO R. P. M. corresponds to maximum scale readings of either 500, 2000 or 8000 It. P. M. In the old types of mechanisms, this result could not possibly have been obtained without separate resistance for each speed range for at the minimum speed the armature would have to be driven at an extremely low and inefficient speed, whereas for the maximum scale deflection the speed of the armature shaft would be so high as to cause not only excessive mechanical wear and possibly damage, but also self induction currents in the armature, thus impairing the accuracy of the indication. Moreover with only one resistance in the circuit of my device the indications are effected by a uniform temperature error whatever the speed 0f the main spindle may be.

This invention is illustrated in the drawings, in which- Figure l is a central longitudinal section through the casing containing the magneto gererator and the speed-change mechanism, an

Fig. 2 is a side elevation of the same device showing the scale-plate on the outside of the casing indicating to which scale range the speed gears are set; and also the millivolt meter.

As shown in the drawings and outlined above, the device consists of an open-ended casing l, having a handle 2, in which casing is themagneto-generator oomprisingtlie U7 shaped permanent magnet 3, thel armature 4, mounted on shaft 5, the eommutator 6, mounted on the outer endV of shaft 5,- and brushes 7. These ybrushes are connected through wires 7 to binding posts 8, projecting through the casing 1, and circuit wires may be therewith connected-to binding `posts 8A of a volt or 'milli-volt meter, M,'"having a triple scale.

Suitably fastened t the open end of the easing l-,is anothercasing 9,1 in. which is mounted the ...speed change.v gearing. This v speed change, mechanismoomprisesthe,main l .f

spindle 10,. vwhich .extends through, casing 9,

4U:andis suitably journaled at ,eaeh .end theref of. Looselyandslidably mounted onshaft 10, is a hub 11,;having a central, gear 12, of

alargediameter andsmaller gears lgand 14 .at Aeach, end thereof, these-last. two; gears being of the same dia1neter-fg'This huh 11,y is f moved along shaft V by means of a yoke 15having a 4threaded horef16,f thro11gh `which, runs athreaded shaftV 17, which is sui'tablyjournaled ateach-end in theeasing 9, andv at vits outerend isaetuatedbyathumb nut 18, to move the yoke lgonewayor another along the shaft 17. yThe upper. end of yoke 15 extends; throughthecasing 9 -and 80., -QUbetweenthe head of which and; thenpper end of yoke 15 isL` held aplateJ lihaving has a bore 19 intoy which ispthreadedasorew thereon graduations 22.` Attached totheoutin mesh.

' side of the easing Q adjaoent the plfatef21 is a plate21 on vwhichxare graduationsvoorre- ,spending to those ou the plate 21and which are .marked with figures, denoting the 1naX mum .speed measured forthat partinularv position of the yoke 15 which ofcourse de.- nOtes the particular setof gears-'which are The armature shaft" 5 extends l through easing 9 and sjOurnaled :therein,

the part .of shaft 5 which ,extends through ,casing 9 v being'of af-larger Idiameterthan the part which is iiieasing 1-and .forrning *.-the jaok shaft of the speed-ehangegearmg,

This lallows of theshaftbeing l,flesigned to properly bear the stresses and wear due to the action of they gears thereon.

Fixedly mounted on. shaft rwithin; the easing 9 and adj aoent,4 the easing 1 isahub .v -,40, havingalarge'and small .gear iand 24 respectively. Loosely mountedronid shaft and also withinv easingy 9 is anotherhub 41, 55,.

onez smallI gear. 27', gear `27.v beingfadjacent F having thereon-A two largej gears f 25, s 26 fand the gear 24 and of the same diameter.1--The two,.large gears. 25 and 26. are also of the same', diameter. Fixedly;y mounted gon; shaft 10 vfand.. journaled within a sleeve-inthe oas- .ing,9is Vagear wheel 28.

The easing 9 is closed fromigthegcasing 1 ysoithat the oilfand lgrease usedffforii lubrs varmature 4.- To properly efeetuate this the shafts 5 and 10 are'mountedy as follows:- Both ends of shaft 5 within casing 9 are -journaled `in @sleeves 29 land y30 respectively, said-sleevesfitting tightly within-their respective apertures in tlie--c'zasing` 9so that any leakage around the same is eliminated. vf The, shaft 10 is likewise journaledinsleeves 32 and v33 which fit tightly within apertures inath ,Qng 9. In order to form a thrust bearing for the shaft 10` when the outer end of. the same is. thruS1againsthrhlffl the .speed offwhielris to henlneasulem I provide within aboreotskeye aiball bearing 34: which ishaokedup by anin 35. threaded-.into the bore. of; sleeve xflrnm; the @Sing .Land v located .in a-. xed postionby laynut 36.

: Inrorder, to proper1y;l 1.1b 'Gate'. theefpilldles 10 ando, Lnrovidefa ruotare asxfollows :Ta eloannel.@5,71V labored nl .casin'g 9 adjaoent .casing l, thrnugh sleeve A30aronnd ;shaft..g 5 andfiurther:in tosleevenand spindle 10. Another J channelA 38,; s-likew-se bored in Casing 9m1- .jaoent sleeve, thimuglo: saiol-V sleeve. around spindle 1Q and into a, space 39 vadtj aoent theendrot sleerefZQ-and "Shaft '5L The openings of these' Qhannlsg Inv GlOSeCl' by l.noeans-f.0fserewsland 44l- The outer end oa p nflleflO isfiprorided 95 with afheadAZ-whohfi 'theoperatimbfithe device is pressed up,.againstl the;,endg- .of. the .rotatingshaft5the;speednoi'hih iS. t0 be j ,measured 1 It rwillloeI readily seen that whenphuball is moved; to the y letyo the.-posit9n.shown in the drawing, the armature 4 will.be .ognneet .ed to shafelQ. through-gears23 1.4,' 12, 27, 25 IM0128. In-this -positoa-ot-thehuh' 11: the armature sadrirenfthrough a @rinsing-.ratio ofigears .by shafta10so as to be-able for i the sameiscale deflection of .thefroltemeter to 'register hgh; speeds-oishaft Whenihub -f 11 is in the mdzfpesiton asashown the drawing, ;the Conneotionbetween armature 4: and .shaft 10. iS-sthr0ugh-gears, 24,;A'12, 2 7?, 25 and 28.1. ,this positen.thearmature registers thefrnedium-- speeds-.of '10 e -the h ubf, .l1 s-'moied-:to: the right-ofthe P0- f-siton .shown athesdrawingfs the.. conneeton betweenthearmaturerfandshaft.l0 is threugh f1, gLIESI 24:, 12,' '13, '2651' 2,5.;31ldi28 121D, P0' v .sition lthe armature..isgoonneoted-fwith shaft 1Q,f tlo'noiigh,` afifhghageararato sosthat it is therebyadapted toregster the-lower, speeds 120 .acoompanying/dra ing fare s ogselectedsithat unfairly-f..to ;.calib1ata.thevoltameterfthrugh 130 the entire range of its deflections for one set of gears when it will be seen that the other gear ratios will be in proper proportion.

The advantages of my improved machine are (l) that it is less costly to make in that, instead of three, only one calibration is necessary; (2) that by selection of suitable change gears, such a maximum armature speed may be selected as lies well within the limits of safe operation and of eiiicient commutation between brushes and commutator; (3) as the range of armature speed remains the same, for all indicated speed ranges, the indications on the volt meter will all be subject to the same temperature errors, if any; and, (4) that the designed machine enables those parts most subjected to wear to be made of suflicient strength; and also lessens the possibility of injury to the electrical mechanism from oil and grease and particles of worn metal thrown oft by the gears.

While I have described my device in detail, it will be understod that my invention is not limited to the use of the particular mechanism described. Obviously, as above indicated, other sets of scale ranges than those shown, and more or less than three such sets may be used, by appropriate changes of gearing. So also, while I have described a milli-volt meter as a suitable indicating instrument, other forms of indicating apparatus, such as are well known in the art may be used.

I claim l. A tachometer device comprising a generator, a main spindle adapted to be rotated by the shaft whose speed is to be measured, an armature shaft, variable speed-change gearing for driving the armature shaft from the main spindle, the gear ratios of said gearing being so chosen that for any position of the change gears a predetermined maximum speed 0f the spindle will correspond to one and the same predetermined vspeed of the armature shaft.

2. A tachometer device comprising a generator, a spindle adapted to be rotated by the shaft whose speed is to be measured, an armature shaft, variable speed change gearing for driving the armature shaft from the spindle and an electric measuring instrument attached to the generator.

3. A. tachometer device comprising a generator, a spindle adapted to be rotated by the shaft whose speed is to be measured, an armature shaft, variable speed change gearing for driving the armature shaft from the spindle, and an electric indicator having a plurality of scales, said scales having range ratios equal to the speed ratios of the speed change gearing;

4. A tachometer device comprising a casing, a partition dividing the casing into two separate chambers, a generator mounted in one of said chambers and having its armature shaft extending into the second chamber, a main spindle mounted in said second chamber and variable speed-changing gearing connecting the main spindle and armature shaft.

5. A tachometer device comprising a casing, a partition dividing the casing into two separate chambers, a generator mounted in one of said chambers and having its armature shaft extending into the second chamber, a main spindle mounted in said second chamber, variable speed-changing gearing connecting the main spindle and armature shaft, and means on the exterior of the casing for indicating the position of the speedchanging gearing.

In testimony whereof I affix my signature.

PETRUS vAN SANTEN KOLFF.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents.

Washington, D. C. 

